Field of the Invention
The invention relates in general to a fingerprint identification electrode structure, and more particularly, to a fingerprint identification electrode structure of a capacitive fingerprint reader.
Description of the Related Art
With progressing technologies, portable electronic devices, such as smart phones, tablet computers and laptop computers, have become essential tools in the daily life. These portable electronic devices provide ever-increasingly diversified functions, and are usually stored with personal information, e.g., phone books, photographs and personal data, which has a certain level of privacy. Although password mechanisms are currently used to prevent portable electronic devices from illegitimate use of others, passwords are prone to exposure and risks of being cracked, and thus yield rather unsatisfactory security. Further, a user is required to memorize a password to use a corresponding electronic device, which may cause user inconveniences. Therefore, means that identifies personal fingerprints for the purpose of identity verification have been developed.
In a conventional capacitive fingerprint reader, a grid structure formed by a plurality of driving electrodes and a plurality of sensing electrodes is used to detect ridges and valleys of a fingerprint to accordingly identify a pattern of the fingerprint. When such conventional capacitive fingerprint reader is incorporated into a portable electronic device, the fingerprint reader is usually disposed below the glass substrate and detects a fingerprint with the glass substrate in between. Although the fingerprint reader is capable of detecting a finger touch, differences between detected signals for ridges and valleys are extremely minute compared to an overall capacitance change caused by the finger. As a result, it is likely that the fingerprint reader incorrectly detects the fingerprint to further lead to a misjudgment. Therefore, there is a need to design a fingerprint reader capable of enhancing the finger identification rate.